1. Field of the Invention
The present invention relates to a signal transmission system, an interface device, and a signal transmission method.
2. Description of the Related Art
Information processing devices such as a notebook personal computer (hereinafter referred to as notebook PC) is operated by application of DC power from a built-in battery or an AC adapter. In the notebook PC, an interface is eliminated or the number of interfaces is decreased for the purpose of miniaturization. In some such notebook PCs, an interface device on which an extension port is mounted is externally connected to extend the interface. Signal transmission is performed between the interface device and the notebook PC by a serial transmission system. In the case of the serial transmission system, data is transmitted after coded. At this point, for example, a Manchester coding system or an AMI (Alternate Mark Inversion) coding system is used as a coding system. For example, Japanese Patent Application Laid-Open (JP-A) No. 1991-109843 discloses a technique of transmitting the data by an AMI code that is of a representative example of a bipolar code. JP-A No. 1991-109843 also discloses a technique, in which a data clock is transmitted while expressed by an intermediate value of a signal level and the data clock is reproduced on the reception side based on the signal level.